When checking your machine to see if you have any instances of PDF2XL installed on your machine, the simplest method is to open Control Panel > Programs > Uninstall a Program and see if it's in the list.
You can also check using the command prompt.
Go to Run > cmd and input this line:
wmic product where "Name like '%PDF2%'" get Name, Version, IdentifyingNumber
Hit your Enter key and wait a few moments (this can actually take a couple of minutes). What you should end up with is one or more lines of information (depending on how many different versions are installed). This also tells you the full version number of the installed applications.